I agree with Mariposa! Older kids, or kids who have decided to 'not like' the presentation part of performance will be harder to teach. It can be taught though!
One of my favorite things to teach is this! You can do this at home too. For starters, I like gymnasts to pick any song with lyrics. Then have them describe the feelings associated with the song. It's easier to do with lyrics. In front of a mirror, we pick a facial expression associated with those feelings. Then we move on to a pose. Then an actual skill where we finish 'in character'. We trade songs and whatnot too for variety. We then move on to composed music with no lyrics. The fun of it is in the play with expression, but all the talk about the emotion that goes into the music is where the learning is. Through it all you may be surprised at what they learn! Some kids end up liking music they thoroughly detested before once they look at it as an experience rather than entertainment.
The other is where they perform their floor routine, but after every tumbling pass and during every pose, they have to find a teammate and make eye contact. The girls can be all over the gym! We cover the performers eyes for 15 seconds while the others scramble to a spot. Once eye contact is made, the girl who she was looking at sits down. It helps them make a connection with their audience, and remember that they are there to make an impression on people. After all, judges are people too! Play it up, mix it up, have fun and turn that routine out! At home you could do this with some dance with their friends, siblings, grandparents, you, your dog, etc!